To accompany the release of Inside Llewyn Davis, the Coen Brothers’ sure-to-be excellent film about the 1960s folk scene in New York, Showtime will air a special called Another Day, Another Time next week. The concert, which was filmed last month in New York, includes rustic performances from the Avett Brothers, Marcus Mumford, Patti Smith, Colin Meloy, Gillian Welch, and Jack White, who dusted off “We’re Going to Be Friends” for the show.